All Publications


  • Temporal Dynamics of Memory-guided Cognitive Control and Generalization of Control via Overlapping Associative Memories. The Journal of neuroscience : the official journal of the Society for Neuroscience Jiang, J., Bramao, I., Khazenzon, A., Wang, S., Johansson, M., Wagner, A. D. 2020

    Abstract

    Goal-directed behavior can benefit from proactive adjustments of cognitive control that occur in anticipation of forthcoming cognitive control demands (CCD). Predictions of forthcoming CCD are thought to depend on learning and memory in two ways: First, through direct experience, associative encoding may link previously experienced CCD to its triggering item, such that subsequent encounters with the item serve to cue retrieval of (i.e., predict) the associated CCD. Second, in the absence of direct experience, pattern completion and mnemonic integration mechanisms may allow CCD to be generalized from its associated item to other items related in memory. While extant behavioral evidence documents both types of CCD prediction, the neurocognitive mechanisms giving rise to these predictions remain largely unexplored. Here, we tested two hypotheses: (1) memory-guided predictions about CCD precede control adjustments due to the actual CCD required to perform, and (2) generalization of CCD can be accomplished through integration mechanisms that link partially overlapping CCD-item and item-item associations in memory. Supporting these hypotheses, the temporal dynamics of theta and alpha power in human electroencephalography data (n=43, 26 females) revealed that an associative CCD effect emerges earlier than interaction effects involving actual CCD. Furthermore, generalization of CCD from one item (X) to another item (Y) was predicted by a decrease in alpha power following the presentation of the X-Y pair. These findings advance understanding of the mechanisms underlying memory-guided adjustments of cognitive control.SIGNIFICANCE STATEMENTCognitive control adaptively regulates information processing to align with task goals. Experience-based expectations enable adjustments of control, leading to improved performance when expectations match the actual control demand required. Using EEG, we demonstrate that memory for past cognitive control demand proactively guides the allocation of cognitive control, preceding adjustments of control triggered by the demands of the present environment. Furthermore, we demonstrate that learned cognitive control demands can be generalized through mnemonic integration processes, enabling the spread of expectations about cognitive control demands to items associated in memory. We reveal that this generalization is linked to decreased alpha oscillation in medial frontal channels. Collectively, these findings provide new insights into how memory-control interactions facilitate goal-directed behavior.

    View details for DOI 10.1523/JNEUROSCI.1869-19.2020

    View details for PubMedID 32019830

  • Dissociable medial temporal pathways for encoding emotional item and context information NEUROPSYCHOLOGIA Ritchey, M., Wang, S., Yonelinas, A. P., Ranganath, C. 2019; 124: 66–78
  • Functional connectivity based parcellation of the human medial temporal lobe NEUROBIOLOGY OF LEARNING AND MEMORY Wang, S., Ritchey, M., Libby, L. A., Ranganath, C. 2016; 134: 123–34

    Abstract

    Regional differences in large-scale connectivity have been proposed to underlie functional specialization along the anterior-posterior axis of the medial temporal lobe (MTL), including the hippocampus (HC) and the parahippocampal gyrus (PHG). However, it is unknown whether functional connectivity (FC) can be used reliably to parcellate the human MTL. The current study aimed to differentiate subregions of the HC and the PHG based on patterns of whole-brain intrinsic FC. FC maps were calculated for each slice along the longitudinal axis of the PHG and the HC. A hierarchical clustering algorithm was then applied to these data in order to group slices according to the similarity of their connectivity patterns. Surprisingly, three discrete clusters were identified in the PHG. Two clusters corresponded to the parahippocampal cortex (PHC) and the perirhinal cortex (PRC), and these regions showed preferential connectivity with previously described posterior-medial and anterior-temporal networks, respectively. The third cluster corresponded to an anterior PRC region previously described as area 36d, and this region exhibited preferential connectivity with auditory cortical areas and with a network involved in visceral processing. The three PHG clusters showed different profiles of activation during a memory-encoding task, demonstrating that the FC-based parcellation identified functionally dissociable sub-regions of the PHG. In the hippocampus, no sub-regions were identified via the parcellation procedure. These results indicate that connectivity-based methods can be used to parcellate functional regions within the MTL, and they suggest that studies of memory and high-level cognition need to differentiate between PHC, posterior PRC, and anterior PRC.

    View details for DOI 10.1016/j.nlm.2016.01.005

    View details for Web of Science ID 000384631300013

    View details for PubMedID 26805590

    View details for PubMedCentralID PMC4955645

  • Post-learning Hippocampal Dynamics Promote Preferential Retention of Rewarding Events NEURON Gruber, M. J., Ritchey, M., Wang, S., Doss, M. K., Ranganath, C. 2016; 89 (5): 1110–20

    Abstract

    Reward motivation is known to modulate memory encoding, and this effect depends on interactions between the substantia nigra/ventral tegmental area complex (SN/VTA) and the hippocampus. It is unknown, however, whether these interactions influence offline neural activity in the human brain that is thought to promote memory consolidation. Here we used fMRI to test the effect of reward motivation on post-learning neural dynamics and subsequent memory for objects that were learned in high- and low-reward motivation contexts. We found that post-learning increases in resting-state functional connectivity between the SN/VTA and hippocampus predicted preferential retention of objects that were learned in high-reward contexts. In addition, multivariate pattern classification revealed that hippocampal representations of high-reward contexts were preferentially reactivated during post-learning rest, and the number of hippocampal reactivations was predictive of preferential retention of items learned in high-reward contexts. These findings indicate that reward motivation alters offline post-learning dynamics between the SN/VTA and hippocampus, providing novel evidence for a potential mechanism by which reward could influence memory consolidation.

    View details for DOI 10.1016/j.neuron.2016.01.017

    View details for Web of Science ID 000373565400021

    View details for PubMedID 26875624

    View details for PubMedCentralID PMC4777629